MRSA Infection (cont.)

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

How is a MRSA infection transmitted or spread?

MRSA infections are contagious from person to person; occasionally direct contact with a MRSA-infected person is not necessary because the bacteria can also be spread by people
who touch materials or surfaces contaminated with MRSA organisms. There are two major ways people become infected with MRSA. The first is
physical contact with someone who is either infected or is a carrier (people who
are not infected but are colonized with the bacteria on their body) of MRSA. The
second way is for people to physically contact MRSA on any objects such as door
handles, floors, sinks, or towels that have been touched by a MRSA-infected person
or carrier. Normal skin tissue in people usually does not allow MRSA infection
to develop; however, if there are cuts, abrasions, or other skin flaws such as
psoriasis (a chronic
inflammatory skin disease with dry patches, redness, and scaly skin), MRSA
may proliferate. Many otherwise healthy individuals, especially children and
young adults, do not notice small skin imperfections or scrapes and may be lax
in taking precautions about skin contacts. This is the likely reason MRSA
outbreaks occur in diverse types of people such as school team players (like
football players or wrestlers), dormitory residents, and armed-services
personnel in constant close contact. A recent example of this spread of MRSA occurred in three NFL football players, all members of the same team, Tampa Bay. Three players got skin infections, and one had to undergo foot surgery to rid the player of recurrent MRSA infection.

How is a MRSA infection diagnosed?

Most doctors start with a complete history and physical exam of the patient to identify any skin changes that may be due to MRSA, especially if the patient or caretaker mentions a close association with a person
who has been diagnosed with MRSA. A skin sample, sample of pus from a wound, or blood, urine, or biopsy material (tissue sample) is sent to a microbiology lab and cultured for S. aureus. If S. aureus
is isolated (grown on a Petri plate), the bacteria are then exposed to different
antibiotics, including methicillin. S. aureus bacteria that grow well when methicillin is
in the culture are termed MRSA, and the patient is diagnosed as MRSA infected.
The same procedure is done to determine if someone is a MRSA carrier (screening
for a carrier), but sample skin or mucous membrane sites are only swabbed, not
biopsied. These tests help distinguish MRSA infections from other skin changes that often appear initially similar to MRSA, such as spider bites and skin changes that occur with Lyme disease. These tests are very important; misidentification of a MRSA infection may cause the patient to be treated with other agents like dapsone (used for spider bites). This can result in progression of the MRSA infection and even other complications due to the dapsone.

In 2008, the U.S. Food and Drug Administration (FDA) approved a rapid blood test
(StaphSR assay) that can detect the presence of MRSA genetic material in a blood sample in as little as two hours. The test is also able to determine whether the genetic material is from MRSA or from less dangerous
forms of staph bacteria. The test (PCR based) is not recommended for use in monitoring treatment of MRSA infections and should not be used as the only basis for the diagnosis of a MRSA infection. In addition, there are new screening tests that report detecting or ruling out MRSA infections in about
five hours.